The present invention relates generally to a vacuum vapor deposition source assembly, and more particularly to a hot-hollow cathode gun source assembly with improved flexibility.
This application is related to the inventor's co-pending patent application Ser. No. 554,414 filed Nov. 22, 1983.
Physical vapor deposition by electron beam evaporation is well known as a method of manufacturing corrosion and oxidation resistant coatings, magnetic coatings, optical coatings, structural and electrically resistive elements, and coatings for subsequent diffusion bonding. Most commercially available electron beam evaporation sources apply several thousand volts at approximately one ampere to a filament cathode to develop the electron beam. However, another source for electron beam evaporation is the hot-hollow cathode, which source generates electrons from an applied voltage of approximately 25 volts and a current on the order of 250 amperes.
The differences inherent in these electron sources causes the electrons produced by each of them to have different current-density and kinetic energy. Only the electrons from the hot-hollow cathode have the desirable density and kinetic energy to ionize the evaporant atoms. These ions may then be used to sputter-clean the substrate prior to deposition, resulting in an excellent adhesion between the coating and substrate. In addition, the hot-hollow cathode has the advantage of high adhesion at a lower substrate temperature than does the filament cathode, eliminating substrate distortion.
Electron beam deposition occurs in a vacuum chamber containing a source, a crucible of material to be deposited, and a substrate upon which the material will be deposited.
Prior hot-hollow cathode installations did not provide for relative movement of gun and crucible; the crucible to substrate distance could only be changed by moving the substrate holding fixture. The radial distance between the crucible and the substrate center line could not be changed, a factor severely limiting the flexibility of a given installation where many different substrates are to be coated.
The inventor's related invention of Ser. No. 554,414 solved many of these problems by permitting movement of the cathode assembly through a hole in the bottom of the vacuum chamber. While this system permitted access to utility supply lines in a nonvacuum environment, and also kept the supply voltage away from conditions within the chamber susceptible to arcing, movement of the gun within the chamber remains limited by the position of the hole and the vertical travel of the assembly.